Initial state QED corrections to W-pair production at LEP2/NLC — Monte Carlo versus semi-analytical approach

We present a comparison of the Monte Carlo code KORALW with the SemiANalytical code KORWAN for W-pair production. We focus on the technical precision, total cross section and some differential distributions. We find the technical precision of KORALW in the LEP2 energy range to be of order 10−4 or better. We show that within the 0.1% precision level the O(α2) photonic corrections are not necessary in the YFS framework, at least for the total cross section. A detailed description of the semi-analytical formalism implemented in the KORWAN routine is also given.